The present invention relates to a thermal management system, and more particularly to a thermal management system which utilizes a fuel stabilization unit and isolates high temperature systems.
Modem aircraft utilize sophisticated Thermal Management Systems (TMS) for thermal management and cooling. In typical modes of operation of the aircraft, lubricating oil, hydraulic fluid, and accessory drives require cooling. At the same time, the avionic systems of the aircraft will require cooling during operation, some by a liquid coolant and others by air. Concurrently, it is generally desirable to heat the fuel delivered to the main propulsion engines to maximize the efficiency of the engine.
Typically, the fuel flow is utilized in combination with a fuel-oil heat exchanger. Although effective, the maximum operating temperature of aviation fuel is limited by a coking temperature limit. Coke deposits may result in a progressive degradation of engine performance.
To minimize this coking condition, the TMS often employs supplemental air-to-liquid heat exchangers that reject heat to either “ram air”, engine fan bypass air flow, and/or “bleed air”.
Ram air is air that is literally rammed into an inlet on the aircraft as a result of the aircraft's forward velocity. A penalty paid for the use of ram air includes system weight and aerodynamic drag. In addition, the installation of ram air circuits in an aircraft so as to convey the ram air to a point of use may be difficult. Moreover, in the case of aircraft intended for military use, ram air inlets may provide an undesirable aircraft radar return.
Fan bypass airflow is air drawn from the fan duct of a gas turbine engine. A penalty paid for the use of bypass airflow for thermal management is the reduction in operating efficiency of the engine.
Bleed air is air taken from the compressor section of the gas turbine engine, whether a main propulsion engine of the aircraft or an auxiliary power unit. A penalty paid for the use of bleed air is a reduction in operating efficiency of the engine from which the air is bled.
Accordingly, it is desirable to provide an effective, lightweight thermal management system which minimizes air-to-liquid heat exchangers.